--- /dev/null
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\HttpKernel;
+
+/**
+ * Signs URIs.
+ *
+ * @author Fabien Potencier <fabien@symfony.com>
+ */
+class UriSigner
+{
+ private $secret;
+
+ /**
+ * Constructor.
+ *
+ * @param string $secret A secret
+ */
+ public function __construct($secret)
+ {
+ $this->secret = $secret;
+ }
+
+ /**
+ * Signs a URI.
+ *
+ * The given URI is signed by adding a _hash query string parameter
+ * which value depends on the URI and the secret.
+ *
+ * @param string $uri A URI to sign
+ *
+ * @return string The signed URI
+ */
+ public function sign($uri)
+ {
+ $url = parse_url($uri);
+ if (isset($url['query'])) {
+ parse_str($url['query'], $params);
+ } else {
+ $params = array();
+ }
+
+ $uri = $this->buildUrl($url, $params);
+
+ return $uri.(false === strpos($uri, '?') ? '?' : '&').'_hash='.$this->computeHash($uri);
+ }
+
+ /**
+ * Checks that a URI contains the correct hash.
+ *
+ * The _hash query string parameter must be the last one
+ * (as it is generated that way by the sign() method, it should
+ * never be a problem).
+ *
+ * @param string $uri A signed URI
+ *
+ * @return bool True if the URI is signed correctly, false otherwise
+ */
+ public function check($uri)
+ {
+ $url = parse_url($uri);
+ if (isset($url['query'])) {
+ parse_str($url['query'], $params);
+ } else {
+ $params = array();
+ }
+
+ if (empty($params['_hash'])) {
+ return false;
+ }
+
+ $hash = urlencode($params['_hash']);
+ unset($params['_hash']);
+
+ return $this->computeHash($this->buildUrl($url, $params)) === $hash;
+ }
+
+ private function computeHash($uri)
+ {
+ return urlencode(base64_encode(hash_hmac('sha256', $uri, $this->secret, true)));
+ }
+
+ private function buildUrl(array $url, array $params = array())
+ {
+ ksort($params, SORT_STRING);
+ $url['query'] = http_build_query($params, '', '&');
+
+ $scheme = isset($url['scheme']) ? $url['scheme'].'://' : '';
+ $host = isset($url['host']) ? $url['host'] : '';
+ $port = isset($url['port']) ? ':'.$url['port'] : '';
+ $user = isset($url['user']) ? $url['user'] : '';
+ $pass = isset($url['pass']) ? ':'.$url['pass'] : '';
+ $pass = ($user || $pass) ? "$pass@" : '';
+ $path = isset($url['path']) ? $url['path'] : '';
+ $query = isset($url['query']) && $url['query'] ? '?'.$url['query'] : '';
+ $fragment = isset($url['fragment']) ? '#'.$url['fragment'] : '';
+
+ return $scheme.$user.$pass.$host.$port.$path.$query.$fragment;
+ }
+}